In motor vehicles, various (electric) motors are usually controlled with the aid of electronic control devices. The control devices typically include a power electronics system that is accommodated, in particular encapsulated or cast, in an electronic housing. Examples of such electronic control devices include actuating motors for automatically adjusting vehicle parts (such as dampers, doors, seats, etc.) or motors of ventilation devices.
Control devices of fan motors are usually attached directly to the vehicle battery without control devices, or the vehicle ignition switch, or other switches situated in between, and are thus permanently connected to the voltage source. In present fan motors, this may be necessary in particular due to the fact that the fans often continue to run for a certain period after the vehicle is switched off (for example, by removing the ignition key).
For control devices of fan motors, the penetration of liquid, typically water, into the electronic housing may be problematic. Since the motor controls are connected directly to the battery voltage without the possibility of being switched off, high currents sometimes flow in the event of a short circuit caused by water, which in the worst case may result in the electronics system and possibly the entire vehicle catching on fire, even when the vehicle is not in operation.
However, penetrating water does not necessarily have to trigger a short circuit. In fact, water may also result in partial functional failures of the electronics system which may be difficult to detect. In particular, water may also result in gradual long-term damage, for example due to corrosion of conductive surfaces.